KR100696017B1 - Extruder Screw - Google Patents

Abstract

The axially stretched extruder screw comprises a screw body having an axially extending extrusion defined by a feed zone at the screw inlet end, a metering zone at the screw outlet end and a fault zone between the feed zone and the metering zone. The first spiral main flight is coaxial with and extends around the screw body along the length of the extruder screw. The second spiral main flight extends somewhat partially along the feed zone to the outlet end of the extruder screw. The fault zone of the extruder screw defines the flights in chapters 1 and 2, which are located between the main flights and in conjunction with them form first and second melt and solid channels extending along the fault zone of the extruder screw.

Extruder * Screw

Description

Extruder Screw             

The present invention relates generally to a machine for processing solid resin materials, and more particularly, to an extruder for mixing and melting the resin materials.

The screw of the extruder used for melting, mixing, and compounding the polymeric resin material typically has three zones, a feed zone, a metering zone, and a melting zone located in the middle of the feed zone and the metering zone. Typically, the screw of the extruder is positioned for rotation in an extruder barrel that includes a hopper region adjacent the feed region of the screw and an outlet end opposite the hopper region and near the metering region of the screw. During operation, the solid resin material is introduced through the hopper region and is present in the feed zone of the screw where the resin material begins to melt. The solid resin material is then transferred to the melting zone where it melts at a higher rate than in the feed zone and ultimately and completely converted to the molten state. The melt is delivered to the metering zone for transport to the discharge end of the extruder where resin material typically passes through the die in the melting zone.

Historically, conventional extruder screws have a single helical flight that is placed in communication with the root or body area of the screw to form a channel through which the resin material introduced into the extruder is thus conveyed. When the resin material is introduced into the melting zone, it begins to melt by heat generated by friction in the resin material itself and heat conducted through the barrel from an external heat source. The molten material forms a molten film that adheres to the inner surface of the extruder barrel. If the thickness of the film exceeds the distance between the extruder barrel and the flight, the leading edge of the flight scrapes the molten film from the barrel inner surface, causing the molten material to form a pool along the flight edge of the flight. . As the resin material continues to melt, a solid mass, usually called a solid layer in the channel, enters the aggregate of solid material and mixes with the pool of molten material.

When this phenomenon occurs, the amount of solid material exposed to the heated barrel is significantly reduced because the solid material is in the form of aggregates entrained in the pool of molten material. Therefore, in order to melt the accompanying solid material, sufficient heat must be transferred to the solid through the molten pool. Since most polymers have good thermal insulation properties, the melt efficiency of the extruder is reduced when the solid layer is broken.

In an effort to improve the melting efficiency, the introduction of a second flight extending around the body of the screw into the melting zone between the advancing surface of the second flight and the retreating surface of the primary flight Extruder screws have been developed to form solid channels as defined in. In addition, a melt channel for conveying the molten material is formed between the receding surface of the second flight and the leading surface of the main flight. The diameter of the root or body region of the screw is gradually increased in the solid channel, thereby decreasing the depth of the channel along the melt zone and decreasing the diameter along the melt channel, thereby increasing the depth of the melt channel. During operation, the molten film formed on the contact surface between the solid layer and the heated barrel surface can move past the second flight into the melt channel to minimize breakdown of the solid layer.

In this type of screw, the melt rate of the solid material is determined by the surface area of the solid layer in contact with the heated barrel wall and the thickness of the molten film formed between the barrel wall and the solid layer. Increasing the surface area of the solid material in contact with the barrel wall results in an improved melt rate by improved heat transfer from the barrel to the exposed side of the solid layer. However, increasing the thickness of the molten film between the solid layer and the barrel causes the molten film to act as a heat insulating material, thereby reducing heat transfer from the barrel to the solid material and lowering the melting rate. Therefore, in order to convert the solid resin material into the molten state, the melting region of such an extruder screw needs to be considerably long, which in turn increases both the manufacturing and operating costs of an extruder using such a screw.

Based on the above, it is a comprehensive object of the present invention to provide an extruder screw which overcomes the problems and drawbacks of the preceding screw. A more detailed object of the present invention is to provide an extruder screw in which the solid material introduced into the screw is melted and mixed in an efficient manner.

Summary of the Invention

The present invention relates to an axially stretched extruder screw having a screw body and an extruded portion extending in the axial direction. The extruder is divided into three zones or zones: the feed zone at the extruder screw inlet end, the metering zone at the screw outlet end and the barrier zone between the feed zone and the metering zone. The first spiral main flight extends from the screw body along the length of the extruder screw and is coaxial with the screw body and has a first leading surface and a first receding surface. The second spiral main flight also extends from the screw body along at least a portion of the feed zone and then along the remaining length of the extruder screw and has a second lead surface and a second retracted surface.

The screw body defines a first helical surface of revolution located between and interlocking with the first leading surface and the second receding surface to define the first solid channel. The screw body also has a second helical rotating surface located between the second leading surface and the first receding surface. The second leading surface and the first receding surface define a second solid channel in conjunction with the second helical rotating surface. The first and second solid channels extend at least along the length of the fault zone of the extruder screw.

In an embodiment of the invention, the fault zone has a third fault surface and a third retracted face and has a first fault flight extending coaxially with the screw body around the screw body along the length of the fault zone. The first obstacle flight is located between the first leading surface and the second retracted surface whereby the first helical rotating surface is redefined between the third leading surface and the second receding surface. As a result of the first barrier flight, the screw body defines a third helical plane of rotation between the first leading surface and the third recessed surface and cooperates with them to form a first melt channel extending along the barrier area.

The second obstacle flight with a fourth leading surface and a fourth retracted surface also extends coaxially with the screw body around the screw body along the obstacle area. The second obstacle flight is located between the second leading surface of the second main flight and the first receding surface of the first main flight, thereby redefining the second helical rotating surface between the fourth leading surface and the first receding surface.

The second obstacle flight also facilitates the creation of a fourth helical face of rotation between the second leading surface and the fourth receding surface and cooperates with them to create a second melt channel extending along the barrier area. Preferably, the pitch of the first and second disturbing flights as well as the pitch of the first and second main flights vary at least along the length of the disturbance area. In a preferred embodiment of the invention, this change in pitch reduces the width of the solid channel in the downstream direction along the fault zone and increases the width of the melt channel. This causes the amount of solids in the solid channel to decrease along the obstructed area in the downstream direction to contact the heated extruder barrel and to melt. In contrast, the width of the increasing melt channel accommodates the increasing melt being transferred therein.

In addition to the change in the width of the melt and solid channels, the depth defined by these channels also changes. For example, the depth of the solid channel may be directed downstream along the obstruction zone to ensure that the continuously decreasing amount of solid resin material therein is adequately sheared and heated to the extruder barrel to promote melting of the resin material. Decreases. In addition, the depth of the melt channel increases in the downstream direction along the fault zone to adequately contain the increase in molten material.

The invention also relates to an extruder comprising an extruder driver to which the extruder screw is rotatably connected. An extruder barrel with an elongated axial bore adjusted to receive the extruder screw is also mounted to the driver. The extruder barrel has a hopper region close to the feed region of the extruder screw to facilitate the supply of solid resin material to the extruder. The axial bore is defined by the axial wall and the axial bore is a plurality of grooves extending around the feed zone of the extruder screw to increase the feed rate and pressure of the solid resin material which again travels downstream along the feed zone It defines.

1 is a side cross-sectional view of an extruder with an extruder barrel and screw according to the present invention.

2 is a partial cross-sectional view of the extruder barrel of FIG. 1 showing the groove defined by the feed zone of the extruder barrel.

3 is a partial side view of the extruder screw of the present invention, which includes a graphical representation of the depth of the solid and melt channels along the screw length.

FIG. 4 is a partial cross sectional view taken along line 3-3 of FIG. 3 showing two solid channels of the feed zone of the extruder screw of FIG.

FIG. 5 is a partial cross-sectional view taken along line 4-4 of FIG. 3 showing two solid channels and two melt channels at the start of the failure zone of the extruder screw of FIG. 3.

FIG. 6 is a partial cross-sectional view taken along line 5-5 of FIG. 3 showing two solid channels and two melt channels of approximately mid-section along the fault zone of the extruder screw of FIG. 3.

FIG. 7 is a partial cross-sectional view taken along line 6-6 of FIG. 3 showing two solid channels and two melt channels at the end of the failure zone farthest from the feed zone of the extruder screw of FIG. 3.

Detailed Description of the Preferred Embodiments of the Invention

As shown in FIG. 1, the extruder, generally designated by reference numeral 10, includes a barrel 12 with a hole 14 defined by a common cylindrical hole wall 16, indicated by dotted lines. Barrel 12 has a hopper region 20 mounted to a suitable driver, for example, but not limited to gearbox 18, and attached to the barrel adjacent to the gearbox. An axially extending extruder screw 22 is located in the hole 14 and rotatably connected to the gearbox 18. The extruder screw 22 comprises three zones or zones, namely a feed zone 24, indicated in the dimension labeled “F” and located at the inlet end 26 of the extruder screw; A metering zone 28, indicated in dimension labeled “M” and located at the outlet end 28 of the extruder screw; And fault zone 30, indicated by a dimension labeled "B" and located between the supply zone and the metering zone.

During operation, the solid resin material is introduced through the feed hopper 32 into the hopper region 20 of the extruder barrel 12. The solid resin material proceeds along the feed zone 24 of the extruder screw 22 where it begins to melt and enters the failure zone 30. As will be described in detail below, the solid resin material is converted into a molten state as it progresses along the obstruction zone 30 and is then supplied to the metering zone 28 defined by the extruder screw 22. The melt, once in the metering zone 28, is generally passed out of the extruder through a die 34 mounted on the outlet end 36 of the barrel 12.

Referring to FIG. 2, the hole wall 16 of the extruder barrel 12 extends in a plurality of axial directions dug into the hole wall extending around the extruder screw 22 for increased pressure and thus increased throughput of the extruder. Groove 38 is defined. During operation of the extruder 10 the groove 38 of the extruder barrel 12 creates a large pressure gradient in the feed zone 24 of the extruder screw 22. This pressure gradient leads to an increase in the material throughput of the extruder.

With reference to FIG. 3, the extruder screw 22 comprises a general cylindrical screw body 40 with an extrusion extending axially along the length of the screw. A first spiral main flight 42 defining a first lead surface 44 and a first retracted surface 46 extends coaxially with the screw body 40 around the screw body 40. In the embodiment shown, the second spiral main flight 48 defining the second leading surface 50 and the second receding surface 52 is also coaxial with the screw body 40 around the screw body 40. Is extended. As shown in FIG. 3, the first and second spiral main flights 42 and 48 start at the inlet end 26 of the extruder screw 22, respectively, and are spaced about 180 ° from each other. However, the present invention is not limited thereto, and the flights may start at an angle other than 180 ° relative to each other. In addition, although each of the first and second spiral main flights 42,48 are shown and described herein, the invention is not limited thereto and a single or two or more main flights may be used without departing from the broader aspects of the invention. Can be.

As shown in FIG. 4, the screw body 40 defines a first helical rotational surface 54, which is the first leading surface 44 and the second retraction of each of the first and second main flights 42 and 48. Interlock with face 52 to form first solid channel 56. Similarly, the screw body 40 defines a second helical rotating surface 57, which is the second leading surface 50 and the first receding surface 46 of each of the first and second main flights 42 and 48. ) Forms a second solid channel 58.

Referring to FIG. 5, in the fault zone B, each of the first and second fault flights 60 and 62 extends from one of the first and second main flights 42 and 48, respectively. Each fault flight 60 and 62 redefines one first and second solid channel 56 and 58 respectively. Thus, the first solid channel 56 is now interlocked with the second receding surface 52 of the second main flight 48, the first helical rotating surface 54 and the leading surface 64 of the first disturbing flight 60. Is formed by. Similarly, the second solid channel 58 is interlocked with the retraction plane 46 of the first helical main flight 42, the second rotational plane 57, and the leading surface 64 of the second obstacle flight 62. Overridden.

The screw body 40 defines a third helical rotational surface 66, which is interlocked with the first receding surface 68 and the third receding surface 68 of the first barrier flight 68 to form the first melt channel 70. Prescribe. Similarly, the screw body 40 defines a fourth helical rotating surface 72, which is interlocked with the second leading surface 50 and the fourth receding surface 74 of the second obstacle flight 62. Two melt channels 76 are defined. As the solid resin material proceeds downstream along the fault zone of each of the first and second solid channels 56 and 58, the resin material melts and moves into the first and second melt channels 70 and 76, respectively. .

As shown in FIGS. 5-7, each of the first and second solid channels 56 and 58 has a progressively decreasing depth along the fault zone in the downstream direction indicated by the arrows marked with a "D" in FIG. 3. , d _s1 and d _s2 . This phenomenon is also represented schematically by the schematic representation 78 of the depth of the solid channel shown in FIG. 3. Similar to the solid channel, each of the first and second melt channels 70 and 76 define depths d _m1 and d _m2 , respectively. However, these depths increase in the downstream direction as represented schematically in the schematic representation 80 of the depth of the melt channel shown in FIG. 3.

In addition to the change in channel depth described above, the pitches of the main flights 42 and 48 and the fault flights 60 and 62 also vary within the fault zone. The change in pitch causes the widths w _m1 and w _m2 defined by each of the first and second melt channels 70, 76 to increase along the fault zone in the downstream direction. At the same time, the depths w s ₁ and w s ₂ defined by the first and second solid channels also change. Thus, as it moves along the barrier area in the downstream direction, the first and second solid channels become narrower and shallower, and the first and second melt channels become wider and deeper.

The operation of the extruder screw 22 of the present invention will be described in detail with reference to FIGS. 1 to 7. Typically, the solid resin material in the form of regrind, pellet and / or powder is introduced into the hopper region 20 of the extruder barrel 12 through the hopper 32. The solid resin material is collected in the first and second solid channels 48 and 58, respectively, and the solid resin material is fed into the feed zone " F " as the extruder screw 22 rotates in the direction of the arrow labeled "R" in FIG. To the fault zone "B". As the resin material moves along the feed region " F ", each of the first and second lead surfaces 44 and 50 of the first and second main flights 42 and 48 are formed so that the solid material is compressed into the solid layer. Bondage inside In addition, the plurality of grooves of the extruder barrel, which are usually temperature controlled, further compress and pressurize the resinous material in the solid channel so that it is transported more quickly and melting starts. This melting action promotes the creation of a molten pool adjacent the leading surface of the main flight of the feed zone of the extruder screw 22.

Once the resin material in the feed zone enters the obstruction zone of the extruder screw 22, it continues melting by a combination of shearing inside the resin material and heat from the extruder barrel 12. The molten material passes over the obstructive flights 60 and 62 to each of the first and second melt channels 70 and 76 from each of the first and second solid channels 56 and 58. This process continues along the fault zone in the downstream direction to the end of the fault zone where the metering zone of the extruder screw 22 feeds molten material through the mold 34.

While the preferred embodiments have been shown and described, various modifications and substitutions are possible without departing from the spirit and scope of the invention. Accordingly, it should be understood that the present invention is illustrative only and not as limiting.

Claims (8)

An axially elongated extruder screw with a screw body comprising a feed zone at the screw inlet end, a metering zone at the outlet end of the screw and an axially extending extrusion defined by a fault zone between the feed zone and the metering zone. In the extruder screw A first spiral main flight around the screw body along the length of the extruder screw, the first spiral main flight having a first leading surface and a first retracting surface; And further comprising a second spiral main flight extending continuously along at least a portion of said feed zone of said extruder screw to said outlet end and having a second leading surface and a second retracting surface, The screw body defines a first helical rotating surface between the first leading surface and the second receding surface and cooperates with them to define a first solid channel, The screw body defining a second helical rotating surface between the second leading surface and the first receding surface and in conjunction with them defining a second solid channel, The failure area, A first barrier flight having a third lead surface and a third recessed surface, the first barrier flight extending coaxially with and around the screw body along the barrier area, wherein the first barrier flight comprises: Being located between the second retracted surfaces such that a first helical rotating surface is redefined between a third leading surface and a second retracted surface, The screw body defines a third helical rotating surface between the first leading surface and the third receding surface and cooperates with them to form a first melt channel extending along the obstacle area, further A second barrier flight having a fourth lead face and a fourth recessed face, the second fault flight extending coaxially with and around the screw body along the fault zone, wherein the second fault flight comprises: Located between the first retracted surface whereby the second helical rotating surface is redefined between the fourth leading surface and the first retracted surface, And an axially elongated extruder screw, said screw body defining a fourth helical rotational surface between said second leading surface and said fourth retracting surface and in connection therewith forming a second melt channel extending along said obstacle area. The extruder screw of claim 1 wherein each of said first and second primary flights defines a pitch that varies along the length of said extruder screw. The extruder screw of claim 1 wherein each of said first and second obstacle flights defines a pitch that varies along the length of said extruder screw. 2. The axially stretched extruder screw of claim 1 wherein each of said first and second melt channels define a depth that gradually increases in a downstream direction along said fault zone. 2. The axially stretched extruder screw of claim 1 wherein each of said first and second solid channels defines a width that gradually decreases along the downstream direction along said barrier area. 2. The axially stretched extruder screw of claim 1 wherein each of said first and second solid channels defines a depth that gradually decreases in the downstream direction along the melt channel. The axially stretched extruder screw of claim 1 wherein each of said first and second melt channels define a width that gradually increases along a downstream direction along said barrier area. Extruder drivers; An elongated extruder barrel mounted to the extruder driver, the elongated extruder barrel having a hopper defined by a hole wall and having a hopper adjacent to the extruder driver to allow introduction of a solid resin material into the hole; An axially stretched extruder screw having a screw body comprising an axially stretched extruded portion defined by a feed zone of the screw inlet end, a metering zone of the outlet end of the screw and a fault zone between the feed zone and the metering zone ; And A plurality defined by the hole wall adjacent the hopper region of the barrel and extending close to the feed region of the extruder screw to increase the feed rate and pressure of the solid resin material in the feed region during operation of the extruder. Grooves; The extruder screw A first spiral main flight around the screw body along the length of the extruder screw, the first spiral main flight having a first leading surface and a first retracting surface; And further comprising a second spiral main flight extending continuously along at least a portion of said feed zone of said extruder screw to said outlet end and having a second leading surface and a second retracting surface, The screw body defining a first helical rotating surface between the first leading surface and the second receding surface and in conjunction with them defining a first solid channel, The screw body defining a second helical rotating surface between the second leading surface and the first receding surface and in conjunction with them defining a second solid channel, The failure area, A first barrier flight having a third lead surface and a third recessed surface, the first barrier flight coaxially extending around the screw body along the barrier area, wherein the first barrier flight and Being located between the second retracted surfaces such that a first helical rotating surface is redefined between a third leading surface and a second retracted surface, The screw body defines a third helical rotating surface between the first leading surface and the third receding surface and cooperates with them to form a first melt channel extending along the obstacle area, further A second barrier flight having a fourth lead face and a fourth recessed face and extending coaxially therewith around the screw body along the fault zone, wherein the second fault flight comprises: the second lead face and Located between the first retracted surface whereby the second helical rotating surface is redefined between the fourth leading surface and the first retracted surface, And the screw body defines a fourth helical rotational surface between the second leading surface and the fourth retracting surface and forms a second melt channel extending in conjunction with the obstruction zone.

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